1. Field of the Invention
The present invention relates generally to personal audio devices such as headphones that include adaptive noise cancellation (ANC), and, more specifically, to architectural features of an ANC system in which the update of one or more acoustical path estimates is tailored to avoid instability due to external changes.
2. Background of the Invention
Telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as personal audio players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise canceling using a reference microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events. Other audio devices may also benefit from noise canceling, or may be provided for the purpose of noise canceling.
Since the acoustic environment around personal audio devices can change dramatically, depending on the sources of noise that are present and the position of the device itself, it is desirable to adapt the noise canceling to take into account such environmental changes. In some cases, adaptive noise canceling circuits can generate undesirable results under certain circumstances.
Therefore, it would be desirable to provide a personal audio device, including a telephone that provides robust noise cancellation that is effective and/or does not generate undesirable responses when external conditions change.